PSI - Issue 70

Anubhav Kumar Singh et al. / Procedia Structural Integrity 70 (2025) 572–579

573

1. Introduction Monitoring of structural health is crucial for guaranteeing the longevity, dependability, and safety of vital structures like bridges, buildings, and industrial facilities. Over time, structures incur various environmental, mechanical and operating stresses, which eventually lead to the development of damage. However, early detection of such damage should enable the prevention of catastrophic failure to minimize the cost of necessary repairs. The conventional techniques of damage detection, like visual inspection and ultrasonic testing fail to yield accurate, efficient, and timely detection of damage in the early stages. Currently there is a growing demand for non destructive testing techniques that provides real-time, reliable information on the condition of a structure. In comparison to traditional visual inspection methods, the introduction of smart materials for monitoring structural health has assisted in more accurate and dependable performance monitoring of the structures. Catastrophic failures can be avoided by using smart materials on the structures to record the initiated harm. In recent decades, engineers and academics have paid close attention to SHM employing the electromechanical impedance (EMI) approach. The most common transducer is a piezoelectric material composed of lead zirconium titanate, which serves as both an actuator and a sensor to measure electromagnetic signals. In recent times, Guangping Li et al. (2023) carried out an effective approach that integrated EMI technology as well as machine learning for monitoring concrete strength with consistent predictions for C30 concrete samples throughout the curing process. Quoc-Bao Ta et al. (2024) conducted concrete stress monitoring using a capsule-like smart aggregate sensor. Demi Ai et al. (2021) conducted experimental as well as numerical assessment to interpret the consequence of heating-time on concrete structures using a PZT sensor. Most studies focused on detecting damage; however, there was a lack of research on how to differentiate between moderate and severe damage. This study evaluates the performance of the EMI technique for detecting moderate and severe structural damage, focusing on changes in dynamic parameters such as the equivalent stiffness of the structural member. The stiffness of the structure is directly linked to the strength, and once it has any damage, the strength is reduced, and subsequently, the stiffness also decreases. Incipient damage is not very significant for the collapse of a structure, but moderate to severe damage will be a sign of the structure collapsing.

Nomenclature d i

Electrical displacement Mechanical strain

M k

E j Electrical field S m Mechanical stress ͞ ⅈ Complex electric permittivity at constant stress of PZT d im , d jk Strain coefficients of PZT E km E Complex elastic compliance at constant electric field Z s,eff Short-circuited effective mechanical impedance of structure u Poisson's coefficient G, B

Real (Conductance) and imaginary (susceptance) components of EM admittance Conductance recorded by the PZT sensor before to structural damage

G i0

G i

Corresponding conductance at the i

th measurement point following damage.

RMSD Root mean Square deviation

1.1. Smart Systems/ Structures

Smart materials are materials that are capable of detecting and responding to changes in their environment, e.g., mechanical loads or environmental conditions. Owing to their capacity to sense and respond to environmental stimuli like temperature, pressure, electric or magnetic fields, chemicals, or even radiation, they are often referred to as "smart" or "intelligent." These interactions may result in changes to their damping characteristics, stiffness, viscosity, or shape.